The present disclosure relates to a vehicle. Particularly, but not exclusively, the present disclosure relates to a tilting vehicle.
As is well known, the amount of road traffic is increasing annually. Much of the increase is due to the increased numbers of passenger cars. Vehicle manufacturers have responded to these problems in part by offering small (“compact” or “sub-compact”) cars. Steadily increasing fuel prices also encourage the use of small cars. There is a limit to the minimum size for a car having conventional seating, motor and wheel arrangements.
A two wheel motor cycle is an alternative to a conventional four wheel car. However, motor cycles have certain drawbacks including safety aspects, a limited luggage-carrying capacity and poor weather protection and the fact that the motorcycle needs to be supported when stationary.
There have been many proposals for three wheel vehicles, whether with two wheels at the front and one wheel at the back or with one wheel at the front and two wheels at the back. Alternatively, very narrow four wheeled vehicles have also been proposed. In a turn, a vehicle experiences an effective force (the “centrifugal force”) which tends to cause the vehicle to roll outwards in a turn. This is not normally a problem in a four wheel vehicle owing to the inherent stability of such vehicles nor is it a particular problem in a motor cycle as the motor cycle is leant into a corner to provide a balance between gravitational and centrifugal forces in a turn.
However, a narrow vehicle with a common hub axle to the rear wheels does not have the inherent stability in a turn of a conventional, wider vehicle. Accordingly, there have been many prior proposals for providing a narrow vehicle which tilts into a corner in order to counteract the centrifugal force.
An example of such a vehicle is shown in US 2008/0238005 to James. This document discloses, in one embodiment, a three-wheeled vehicle having rear cross arms forming a parallelogram shape which extend across the width of the vehicle between the rear wheels. The vehicle chassis, together with the vehicle rear wheels, can be tilted by skewing the parallelogram-shaped cross arms in one direction or the other to assist the vehicle during cornering. This document also discloses a mechanical front parallelogram tilting arrangement in an embodiment which comprises a pair of front wheels together with a single rear wheel.
An alternative construction of tilting vehicle is disclosed in GB 2444250 to Shotter. This document discloses a tilting vehicle with a hydraulic damper arrangement connected to the rear wheels. The hydraulic dampers on each wheel are mechanically connected by a cross bar. In one mode of operation, the dampers operate independently of one another, the tilting operation being achieved through the movement of the cross bar. In another mode of operation, the dampers are interconnected and arranged to move in the same direction to prevent differential movement. GB 2444250 relates to a narrow-track vehicle without a fully-enclosed cabin. However, the disclosed arrangement is structurally complex and the rider-controlled lean and splayed front swingarm suspension arrangement is considered unsuitable for a heavier, fully enclosed two-seater vehicle at high speed and under braking.
A further alternative construction of tilting vehicle is disclosed in WO99/61302 to Jackson. In one embodiment, a three wheel vehicle is shown and described which has a pair of rear suspension struts, each carrying a rear wheel. The struts provide suspension functions together with enabling the vehicle to tilt.
Other known tilting mechanisms for three wheel vehicles rely on the rider/driver deliberately actuating levers which are connected to a mechanism to make the vehicle tilt; such mechanisms are often heavy and require the driver to learn how to operate the levers as such lever operated mechanisms are not at all intuitive.
An example of a four wheeled tilting vehicle is disclosed in WO-A-2006/003489 to Moulene. In this document, a purely mechanical tilting front wheel arrangement is disclosed. A further example is given in EP1702773 to Harty and Kemp.
Accordingly, there is a perceived need to provide a fully enclosed vehicle which can be small, preferably with three or four wheels, and which can tilt into a turn either by virtue of a familiar, passive mechanism which is easy and preferably intuitive for the driver to operate, or by intuitive electronic control.
Further, narrow passenger vehicles comprise, by their very nature, extremely limited interior space. In known arrangements, the space between the rear wheels of these vehicles is taken up with the mechanisms to enable the vehicle to tilt. Therefore, there exists a technical problem that known tilting narrow passenger vehicles do not make efficient use of the available space within the vehicle.